The present disclosure relates, inter alia, to compositions and methods for treating viral diseases and cancer. In one aspect it relates to lipophilic antiviral and anticancer acyclic nucleoside phosphonate diesters, preparation thereof, and methods of using the compounds to treat viral diseases and cancer.
Viruses are infectious particles that can replicate their DNA and RNA only within host cells. Viral infections may lead to mild or severe illnesses in humans and mammals. Examples of viral infections include hepatitis B and C, smallpox, herpes simplex, cytomegalovirus, human immunodeficiency virus (HIV), influenza, adenovirus, chickenpox, BK virus, JC virus and precancerous lesions caused by infections with the human papillomavirus (cervical intraepithelial neoplasia, vaginal and anal intraepithelial neoplasia). Viral infection may also lead to cancer in humans and other species. Viruses known to cause cancer include but are not limited to human papilloma virus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), HIV and Epstein Barr virus (EBV). Vaccination has been successful in preventing infection from many viruses. Antiviral agents are known that interfere with viral DNA or RNA synthesis and viral replication and are used to prevent or treat viral infections in mammals and humans. For example, combinations of antiviral drugs are used to treat AIDS, hepatitis B, hepatitis C, herpes simplex viruses, cytomegalovirus and influenza. Despite these successes, viral diseases remain an important public health problem and improved antiviral agents and anticancer agents are needed. For example, there is presently no approved antiviral treatment for human papillomavirus infections.
Many antiviral drugs are nucleoside or nucleotide analogs. Examples of antiviral nucleoside analogs include azidothymidine, acyclovir, ganciclovir, lamivudine and emtricitabine. Acyclic nucleoside phosphonates (ANPs) are a class of nucleotide analogs and are effective antiviral agents. Adefovir, tenofovir and cidofovir are ANPs that have been approved for clinical use against human infections with HBV, HIV and CMV, respectively.
ANPs are known in the art not to be absorbed readily from the gastrointestinal tract of mammals because of their molecular weight and the presence of the double negative charge on the phosphonate. Because of their poor oral pharmacokinetic properties, ANPs are usually converted to prodrugs to produce clinically useful therapeutic agents. It has been demonstrated that masking one or both negative charges with promoieties improves the uptake and transport into the small intestinal enterocytes where the promoiety is cleaved, releasing the ANP into the circulation; examples include tenofovir disoproxil fumarate and adefovir dipivoxil. Another approach is to prepare alkoxyalkyl or alkyl monoesters of ANPs to increase oral bioavailability of the drug. With the alkoxyalkyl ANP monoester approach, side effects may occur when non-targeted tissues such as the small intestine are overexposed. For example, in enterocytes, enzymatic cleavage of the promoiety by a phospholipase C or an acid sphingomyelinase to the ANP may result in local toxicity because of further anabolic phosphorylation to the ANP diphosphate which may inhibit enterocyte DNA synthesis. Lipophilic ANP diester compounds of the invention are anticipated to undergo less cleavage from intact prodrug to ANP in the small intestine enterocytes following oral administration reducing GI side effects and releasing more drug substance into the circulation and producing higher levels of the drug substance in the blood.
ANPs or their alkyl or alkoxyalkyl monoesters may exhibit limited uptake in certain target tissues such as the central nervous system. An additional advantage of nucleoside phosphonate diesters is the masking of the remaining negative charge on the phosphonate oxygen with a second masking group which can increase penetration of the drug substance into the central nervous system (CNS) for treatment of CNS viral infections (for example, HIV or JC virus) or for treatment of brain cancers such as glioblastoma. Cancer cells rapidly synthesize DNA and undergo uncontrolled cell division. The lipophilic acyclic nucleoside phosphonate (ANP) diester compositions described herein can be metabolized to their diphosphates which inhibit or block DNA synthesis and cell division in target cancer cells, leading to cell death while having substantially lesser effects on non-malignant cells. Exposure of various types of cancer cells to acyclic nucleoside phosphonates diesters of the invention may result in much greater cytotoxicity than that observed in normal non-malignant cells. For example, leukemias, lymphomas, brain neoplasms such as glioblastoma and cervical cancer cells may be more susceptible to the cytoxic effects when exposed to lipophilic ANP diesters than the corresponding non-malignant cell lines. Lipophilic acyclic nucleoside phosphonate diesters exhibit more selective toxicity, improved access to the central nervous system and effective topical uptake for treatment of skin cancers, viral skin infections, cervical intraepithelial neoplasia (CIN), vaginal and anal intraepithelial dysplasia, venereal warts and related infections caused by the human papillomavirus when compared to acyclic nucleoside phosphonate monoester compositions.
Compounds disclosed herein having both ANP phosphonate negative charges masked with functional groups provide for more effective use as topical agents for treatment of skin cancers and viral infections. In particular, compounds disclosed herein provide for efficacious treatment for infections of the cervical, vaginal, rectal and penile epithelium with the human papilloma virus including the high risk subtypes such as 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, 82 which are associated with cervical, rectal, penile and vaginal cancer and venereal warts.